Implicit None return value is not type checked

[suutari-ai]

I think this is a bug in Mypy. Mypy doesn't seem to check the type of the implicit None return value of a function which doesn't have a return statement.

$ cat foo.py 
def foo() -> str:
    pass
$ mypy --strict foo.py

• What is the actual behavior/output?

No errors reported.

• What is the behavior/output you expect?

foo.py:2: error: Incompatible return value type (got "None", expected "str")

• What are the versions of mypy and Python you are using?

mypy 0.701
Python 3.6.5

• Do you see the same issue after installing mypy from Git master?

Haven't tested.

• What are the mypy flags you are using? (For example --strict-optional)

--strict

[ilevkivskyi]

Empty (trivial) function bodies are special, see #2350.

You can try adding something else there to see an error about missing return statement.

[suutari-ai]

Ah, I see. Thanks for the info!